Variable reflectance cover

ABSTRACT

A variable reflectance cover for a sranning system. The cover comprises a backing moveable through a plurality of positions. Moving the backing through the plurality of positions varies the reflectance of the cover. In one embodiment, the backing is an endless rotatable belt. In a second embodiment, the backing is a removable panel having a first side with a first reflectance and a second side with a second reflectance. In yet a third embodiment, the backing includes polarizers placed adjacent to a reflective panel. Rotating one polarizer relative to another varies the reflectance of the cover.

FIELD OF THE INVENTION

[0001] The present invention relates to a cover for a scanning system,and more particularly to a cover with a variable reflective backing.

BACKGROUND

[0002] An optical scanner is used to generate an electronic file, abitmap file for example, which is representative of a scanned objectsuch as a document or photograph. This is typically accomplished bypassing a controlled light source across the surface of the object.Light reflects off the surface of the object and back onto an array ofphotosensitive devices such as a charge coupled device, or CCD, array.As the light source passes over the object, the CCD array converts thereflected light intensity into an electronic signal that is ultimatelydigitized into an electronic file once the entire object is scanned.

[0003] In a conventional flatbed scanner, the light source and CCD arrayare located in a base covered by a plane of transparent glass. Theobject being scanned is placed, or sandwiched, between the glass planeand a cover. The inside surfaces of some covers are constructed of ahigh reflectance white material. The high reflectance white surfaceenables the conventional scanner to reduce or eliminate dark bordersaround the document, black circles where punch holes exist, and darkborders around multiple images such as multiple receipts on a singlescan. Moreover, the high reflectance white surface enables theconventional document scanner to improve the contrast of the document'simage by reflecting the light that is transmitted through the objectback to the CCD array. For example, when scanning a transparency, thelight passing through the transparency reflects off the white cover andis detected by the CCD array.

[0004] Although a high reflectance white surface will allow aconventional scanner to eliminate unwanted dark areas, this whitesurface limits the ability of the conventional scanner. Morespecifically, scanners have the ability to detect the location of theobject being scanned. This detection enables the scanner to provideelectronic registration and electronic skew correction. Moreover, thedetection of the location of the object's edges enables the scanner toprovide automatic magnification selection. However, this edge detectiondepends upon the ability of the scanner to sense the difference in thereflectance between the object and the cover. Thus, some objects wouldbetter be scanned with a black rather than white background on thecover.

[0005] A scanner with this low reflectance background cover allows forreliable edge detection, but the same background fails to suppress theblack borders or punch holes. Moreover, the low reflectance backgroundprovides very low contrast when attempting to scan objects such astransparencies or semi opaque objects.

[0006] Since there are problems with using just a high or a lowreflectance background with a scanner, a scanner with at least two modesof reflectance is ideal. Liquid crystal display technology has been usedfor scanning systems to provide a set of reflectance options. Thesescanning systems offer a good solution to the problem, but they areexpensive. Also, if a problem arises with the liquid crystals it is noteasy or inexpensive to repair. In many cases it is less expensive topurchase a new scanner rather than attempting to repair a liquid crystalcover.

SUMMARY

[0007] The present invention is directed to a variable reflectance coverfor a scanning system. The cover comprises a backing moveable through aplurality of positions. Moving the backing through the plurality ofpositions varies the reflectance of the cover. In one embodiment, thebacking is an endless rotatable belt. In a second embodiment, thebacking is a removable panel having a first side with a firstreflectance and a second side with a second reflectance. In yet a thirdembodiment, the backing includes polarizers placed adjacent to areflective panel. Rotating one polarizer relative to another varies thereflectance of the cover.

DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a perspective view of a flat bed optical scanner with aconventional cover.

[0009]FIG. 2 is a side view of the scanner of FIG. 1 having a cover witha high reflectance backing.

[0010]FIG. 3 is a side view of the scanner of FIG. 1 having a cover witha low reflectance backing.

[0011]FIGS. 4 and 5 are side views of a cover having a rotatable endlessbelt with high and low reflectance sections. In FIG. 4, a highreflectance section is positioned adjacent to a scanning surface. InFIG. 5, a low reflectance section is positioned adjacent to a scanningsurface.

[0012]FIG. 6 is a side view of the cover of FIGS. 4 and 5 wherein theendless belt is rotated by a motor.

[0013]FIG. 7 is a side view of an endless belt with an increasedcircumference.

[0014]FIG. 8 is an isometric view of a cover having a removable panel.

[0015]FIG. 9 is a top plan view of a cover having adjacent rotatablepolarizers.

[0016]FIG. 10 is a section view taken along the line 10-10 in FIG. 9wherein the adjacent polarizers allow light to pass through and reflectoff the backing.

[0017]FIG. 11 is a section view taken along the line 11-11 in FIG. 9wherein the adjacent polarizers are rotated to absorb light beforereaching the backing.

[0018]FIG. 12 is a section view of the cover of FIG. 9 including a motorfor rotating one of the polarizers.

DETAILED DESCRIPTION

[0019] FIGS. 13 illustrate a conventional scanner 10 used in conjunctionwith a computer system (not shown) for acquiring an electronic image ofan object 12 (shown in FIGS. 2 and 3) such as a photograph or textdocument. Scanner 10 generally includes housing 14 containing guide 16allowing linear movement of scanner carriage 18. Carriage 18 is mountedbelow a transparent scanning surface 20 that supports object 12. Toilluminate object 12 carriage 18 includes lamp 22 and reflector 24. Lamp22 and reflector 24 are mounted in carriage 18 to focus light up throughscanning surface 20 onto object 12. Scanner 10 also includes cover 26having backing 28.

[0020] Referring to FIGS. 2 and 3, an object 12 to be scanned is placedon scanning surface 20 and cover 26 is closed sandwiching object 12between scanning surface 20 and backing 28. With lamp 22 illuminated,carriage 18 passes linearly underneath object 12. Light from lamp 22reflects off object 12 back onto an array of photosensitive devices suchas a charge coupled device (CCD) array 30 in carriage 18. Discerning theintensity of the reflected light, CCD array 30 generates an electricalsignal allowing the computer system to produce a digitizedrepresentation of object 12.

[0021] Some light also reaches backing 28. This occurs in areas outsidethe edges or within punch holes of object 12. Where object 12 istransparent or opaque, some light passes directly through object 12reaching backing 28. The backing 28 illustrated in FIG. 2 is constructeda high reflectance and generally light colored or white material.Consequently, much of the light reaching backing 28, either directly orthrough object 12 is reflected back to CCD array 30. The backing 28′illustrated in FIG. 3 is constructed from a low reflectance andgenerally dark or black material. Consequently, much if not all of thelight reaching backing 28′ is absorbed rather than reflected.

[0022] Referring now to FIGS. 4-12, the present invention lies in theconstruction of cover 40. In the embodiment illustrated in FIGS. 4-7,backing 42 is an endless belt 44 rotatable around tension rollers 46 and48 and partially enclosed within shell 50. Endless belt 44 has a firsthigh reflectance section 52 and a second low reflectance section 54. Forexample, first section 52 may be white, while second section 54 may beblack. In FIGS. 4 and 5, crank 56 coupled to tension roller 48 allowsendless belt 44 to be manually rotated into a desired position.Referring to FIG. 6, endless belt 44 may instead be automaticallyrotated by motor 58 engaging tension roller 48. It is envisioned thatmotor 58 will be a stepper motor accurately directed by a series ofelectrical pulses generated by controller 60. Advantageously, endlessbelt 44 can be easily removed and replaced when damaged or interchangedwith another belt having sections with different levels of reflectance.

[0023] With first section 52 rotated into place adjacent to object 12,as shown in FIG. 4, light reaching first section 52 is reflected back toCCD array 30. With cover 40 closed and second section 54 rotated intoplace adjacent to object 12, light reaching backing 42 is absorbedrather than reflected. Alternatively, endless belt 44 may have more thantwo sections each having a specified reflectance. For example, inaddition to including high and low reflectance sections, endless belt 44can include additional sections having varying levels of reflectance.The possible combinations are infinite. The increased area needed foradditional sections can be obtained by increasing the circumference ofendless belt 44. This increased circumference can be managed withadditional tension rollers 62, 63, and 64 as illustrated in FIG. 7.

[0024] In the embodiment of cover 40 illustrated in FIG. 8, backing 42is a removable panel 66 held in a slot created by grips 68 and 70. Panel66 has a first side 72 having a first reflectance and a second side 74having a second reflectance. With cover 40 open, panel 66 can bemanually removed and replaced so as to expose either the first or thesecond side 72 or 74. For example, first side 72 may be white and secondside 74 may be black. Where a backing with a high reflectance isdesired, panel 66 is placed between grips 68 and 70 such that first side72 is exposed. When cover 40 is then closed, first side 72 will beimmediately adjacent to the object being scanned. When a backing with alow reflectance is desired, panel 66 is removed and replaced such thatsecond side 74 is exposed. Panel 66 can be easily replaced if damaged orcan be interchanged with another panel when other reflectance levels aredesired.

[0025] In the embodiment of cover illustrated in FIGS. 9-12, backing 42includes a first polarizer 76, second rotatable polarizer 78 affixed toreflective panel 80. Polarizers 76 and 78 are rotatable relative to oneanother in order to vary the amount light from lamp 22 that reachesreflective panel 68. Light can be represented as a transverseelectromagnetic wave. Imagine, for example, a length of rope held by twochildren at opposite ends, the children begin to displace the ends ofthe rope in such a way that the rope moves in a plane either up anddown, left and right, or any angle in between. Ordinary white light ismade up of such waves that fluctuate at all possible angles.

[0026] Light is considered to be linearly polarized when it containswaves that only fluctuate in one specific plane. It is as if the rope inthe example is strung through a picket fence. The wave can only move upand down in a vertical plane. A polarizer is a material that only allowsonly light with a specific angle of vibration to pass through while itabsorbs the rest. The direction of fluctuation passed by the polarizeris referred to as the polarizer's optical axis. If two polarizers areset up in series so that their optical axes are parallel, light passesthrough both. However, if the polarizers are rotated relative to oneanother until their optical axes are perpendicular, the polarized lightpassing through the first will be absorbed by the second. As thepolarizers are rotated in relation to one another and the angle betweentheir optical axes varies from zero to ninety degrees, the amount oflight passing through both polarizers decreases proportionally.

[0027] In FIG. 10, the optical axes of the first and second polarizers76 and 78 are parallel. In FIG. 11, polarizer 78 is rotated until thoseaxes are perpendicular to one another. FIG. 10 illustrates theconfiguration generating a maximum effective reflectance with thegreatest amount of light reaching reflective panel 80 and reflectingback to CCD array 30. FIG. 11, on the other hand, illustrates theconfiguration producing a minimum effective reflectance with polarizers76 and 78 absorbing all light before it reaches reflective panel 80. Theeffective reflectance can be tuned to any desired level between theminimum and maximum levels by adjusting the angle between the opticalaxes of polarizers 76 and 78.

[0028] In the embodiment illustrated in FIGS. 9-11, second polarizer 78and attached reflective panel 80 are manually rotated using dial 82.Dial 82 includes knob 84 coupled to shaft 86 passing through shell 50.Shaft 86 is then coupled to reflective panel 80. Turning knob 84 rotatesreflective panel 80 and the attached second polarizer 78. In oneversion, dial 82 may also include lever 88 and gauge 90. Lever 88extends radially outward from knob 84 across the surface of shell 50allowing for a more accurate rotation and placement of second polarizer78. Lever 88 is placed such that when it points to one end of gauge 90,the optical axes of polarizers 76 and 78 are parallel. When lever 88 isrotated so that it points to the other end of gauge 90, the optical axesof polarizers 76 and 78 are perpendicular. Cover 40 may include stops 92for holding dial 82 and joined second polarizer 78 stationary in one ofmany predetermined positions. Alternatively, second polarizer 78 can beautomatically rotated by motor 94 as illustrated in FIG. 12. It isenvisioned that motor 94 will be a stepper motor accurately directed bya series of electrical pulses generated by controller 96.

[0029] Although the invention has been shown and described withreference to the foregoing exemplary embodiments, it is to be understoodthat other embodiments are possible, and variations of and modificationsto the embodiments shown and described may be made, without departingfrom the spirit and scope of the invention as defined in followingclaims.

What is claimed is;
 1. A variable reflectance cover for a scanning system, comprising a backing moveable through a plurality of positions, wherein moving the backing through the plurality of positions varies the reflectance of the cover.
 2. The cover of claim 1, wherein the backing is an endless rotatable belt.
 3. The cover of claim 2, wherein the endless rotatable belt comprises a plurality of sections each having a specified reflectance, such that as the backing is moved through each of the plurality of positions, a different section is at least partially exposed.
 4. The cover of claim 3, wherein the endless rotatable belt comprises a first section having a first reflectance and a second section having a second reflectance different from the first reflectance.
 5. The cover of claim 4, wherein the first section is white and the second section is black.
 6. The cover of claim 2, wherein the endless rotatable belt is interchangeable with other endless rotatable belts.
 7. Tho cover of claim 2, further comprising a manual crank operative to selectively rotate the belt though each of the plurality of positions.
 8. The cover of claim 2, further comprising a motor operative to selectively rotate the belt though each of the plurality of positions.
 9. The cover of claim 8, further comprising a controller placed in electrical communication with the motor, the controller being configured to direct the motor to selectively rotate the bolt in to one of the plurality of positions.
 10. The cover of claim 1, wherein the backing is a removable panel moveable between a first position in which a first side of the panel is at least partially exposed and a second position in which a second side of the panel is at least partially exposed.
 11. The cover of claim 10, wherein the first side has a first reflectance and the second side has a second reflectance different from the first reflectance.
 12. The cover of claim 11, wherein the first side is white and the second side is black.
 13. A variable reflectance cover for a scanning system, comprising: a plurality of adjacent polarizers, at least one of the polarizers being rotatable in relation to another polarizer; and a reflective panel located adjacent to the polarizers; wherein rotating one of the polarizers alters the reflectance of the cover.
 14. The cover of claim 13, wherein at least one of the polarizers is detachable from the cover.
 15. The cover of claim 13, further comprising a mechanical dial operatively connected to one of the polarizers, the dial when manually rotated causes the connected polarizer to rotate in relation to another polarizer.
 16. The cover of claim 13, further comprising a motor operative to selectively rotate one of the polarizers in relation to another polarizer.
 17. The cover of claim 16, further comprising a controller placed in electrical communication will with motor, the controller being configured to direct the motor to accurately rotate one of the polarizers in relation to another polarizer.
 18. A variable reflectance cover for a scanning system, comprising: a shell; an endless belt rotatable around a tensioning roller and at least partially enclosed within the shell, the belt comprising a plurality of sections, each section having a specified reflectance; and a manual crank operatively coupled to the tensioning roller, the crank operative to rotate the endless belt and to at least partially expose a selected section.
 19. A variable reflectance cover for a scanning system, comprising: a shell; and a removable panel having a having a first side with a first reflectance and a second side with a second reflectance, the panel selectively held against the shell with either the first or second side being at least partially exposed.
 20. A variable reflectance cover for a scanning system, comprising: a shelf; two adjacent polarizers, at least one of the two polarizers being rotatable in relation to the other polarizer; and a reflective panel located adjacent to the polarizers and between the polarizers and the shell; wherein the polarizers and the reflective panel are at least partially contained within the shell and rotating one of the polarizers alters the reflectance of the cover. 